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Can You Get Vitamin D From the Sun After 4 PM & Tips for Effective Sun Health

Can you get Vitamin D from the sun after 4 PM? Discover the facts and practical tips for safe and effective sun health habits.

Everyone knows sunlight is excellent for your health, especially when getting enough vitamin D. But what if you miss sun exposure earlier in the day? Can you get vitamin D from the sun after 4 PM? This can be an essential question to answer if you’re trying to optimize your vitamin D levels.

This guide will offer valuable insights to help you achieve your goals, like optimizing your sun exposure for maximum health benefits while maintaining skin safety and ensuring you get enough vitamin D. But, How to Measure Sun Exposure?

One way to get started is to track your daily sunlight exposure to ensure you get enough for your health. SunSeek's daily sunlight exposure tracker can help you do just that. This easy-to-use tool enables you to optimize your sun exposure for vitamin D while avoiding excessive sunlight that can harm your skin.

How Much Vitamin D Do You Get From the Sun?

child in a forest - Can You Get Vitamin D from the Sun After 4 PM?

Vitamin D is sometimes called the sunshine vitamin because sunlight is one of the best sources of this essential nutrient. Our bodies make vitamin D when our skin is exposed to UVB (ultraviolet B) rays from the sun (or artificial UVB lamps). When UVB rays hit the skin, a form of cholesterol called 7-dehydrocholesterol in the plasma membranes of skin cells absorbs UVB photons. This process transforms 7-dehydrocholesterol into an inactive form of vitamin D called pre-vitamin D3 or precalciferol. Previtamin D3 converts into vitamin D3 (cholecalciferol), which is then metabolized in the liver to 25-hydroxyvitamin D3, the circulating form found in the blood. Next, vitamin D is activated in the kidneys to its biologically active form, 1,25-dihydroxyvitamin D3. As we don’t get much vitamin D from food, sunlight is the primary method for boosting or maintaining its levels. People with more sun exposure have higher blood vitamin D levels than those with more time inside.

Factors that Affect Vitamin D Production from Sun Exposure

The short answer to how much vitamin D you can get from the sun is that it depends. Several factors can impact vitamin D synthesis, most outside our control.

Geographic Location

Where you live affects how much vitamin D you can get from sun exposure. People living closer to the equator can get vitamin D year-round by accessing intense UV radiation. Conversely, people who live far from the equator may not get enough vitamin D from sunlight in the fall and winter months. The sun's angle at these latitudes prevents sufficient UV radiation from penetrating the atmosphere to reach the skin.

Skin Tone

Your skin tone affects how much vitamin D you can get from sun exposure because melanin, the pigment that gives skin its color, reduces the skin’s ability to make vitamin D. Therefore, fair-skinned individuals can produce vitamin D more quickly than darker skin. While people of all skin tones should get sun exposure to help maintain healthy vitamin D levels, those with darker skin should take extra precautions to avoid insufficient levels, especially if they live in northern latitudes or areas with limited sunlight.

Time of Day

Time of day affects how much vitamin D you can get from sun exposure because the sun’s angle impacts UV radiation levels. UV radiation is most intense when the sun is directly overhead, which occurs around midday. At this time, a person’s risk of developing a sunburn is lowest, and they can safely produce vitamin D more quickly.

Season

As mentioned earlier, the season can affect how much vitamin D you can get from sun exposure. UV radiation levels are much higher in the summer than in the winter so you can produce vitamin D more quickly and efficiently. In the fall and winter months, you may need to spend more time in the sun to achieve adequate vitamin D levels in your blood, especially if you live at higher latitudes.

Duration of Exposure

The amount of time you need to spend in the sun to produce vitamin D varies from person to person. As a general rule, the lighter your skin, the less time you need to spend in the sun to produce vitamin D. Those with darker skin tones may require up to 30 minutes or longer of sun exposure to produce adequate vitamin D levels.

Research on Vitamin D Production from Sun Exposure

Several studies have assessed vitamin D production from sunshine exposure. First, a study in Switzerland found that just 10-15 minutes of sun exposure in the spring and summer, with 22% of skin exposed, led to the production of 1,000 IU of vitamin D. During these warmer seasons, the time between sunburn risk and producing 1,000 IU of vitamin D ranged from 9 to 46 minutes. This means that some people are at a greater risk of developing harmful sunburns before they reach adequate vitamin D production. During the fall and winter, up to 6.5 hours of sun exposure (with 8-10% of the skin surface uncovered) was required to achieve the same vitamin D levels, which increases the risk of sunburn or sun damage. For reference, the face accounts for approximately 9% of the body’s surface, each arm is 9%, each leg is 18%, and the abdomen and back are 18% each.

Synthesis Rate

Sunnier environments accelerate vitamin D synthesis, allowing the body to produce ~1,000 IUs within just a few minutes. It’s generally recommended that you expose yourself to sunlight for 50% of the time it would take you to develop a mild sunburn or slight pinkness that remains 24 hours later—this is called the “minimal erythemal dose,” or MED. Exposing the whole body (like in a bathing suit) to 0.5 MED of UVB radiation (meaning it did not cause sunburn) has been shown to synthesize 7,000 to 10,000 IU of vitamin D. As everyone’s MED is different, the time this takes would vary depending on how quickly you tend to burn.

Vitamin D Production in Fair-Skinned Adults

Research has shown that fair-to-medium-skinned adults in bathing suits who were exposed to 0.5 MED of UV radiation just once per week for 3 months increased their serum vitamin D levels by 125-200%. In comparison, adults who took 1,000 IU of supplemental vitamin D daily during that time increased their blood levels by about 50%. This study in Australia found that summertime sun exposure for 2 to 14 minutes at noon (three to four times per week with 15% of the body exposed) produced up to 600 IU of vitamin D (the Recommended Dietary Allowance) in fair-skinned people.

However, sunburn was found to occur in as little as 8 minutes—again, meaning that some people might not get enough vitamin D without burning first. To circumvent this, some researchers recommend getting sunshine little and often, which could mean 5 minutes of exposure at a time, a few times daily. In the winter, when only your face and hands are exposed, it may take up to 6 hours of sun exposure during peak hours for your skin to produce sufficient vitamin D, so a vitamin D supplement is often recommended during the cooler months. It’s estimated that 5 to 15 minutes of sun exposure with 25% or more of your body exposed at least three times a week during peak hours (11 a.m. to 3 p.m.) is likely adequate to maintain healthy blood vitamin D levels. If you have dark skin, you may need up to 30 minutes.

Can You Get Vitamin D from the Sun After 4 PM?

Late-Day Sunshine: Can You Still Get Vitamin D from the Sun After 4 PM?

When it comes to vitamin D production, timing is everything. The best time to get vitamin D from the sun is midday when the sun is high in the sky, and UVB rays are the strongest. For most regions, this is between 10 a.m. and 2 p.m. However, depending on your location and the time of year, there may be opportunities to boost your vitamin D levels even after 4 p.m. Sun exposure after 4 p.m. may not be as practical as catching rays at midday, but it can help if you cannot get outside during the day. The UVB rays that produce vitamin D are present until sunset, so even if you’re outside late in the afternoon, there’s a chance you’ll get some exposure before they diminish. The amount of UVB rays left in the afternoon depends on several factors, including location, the season, and the current weather conditions. For instance, if you live in a region that has recently experienced a winter season, you may have to wait until late summer to get adequate UVB rays again. Furthermore, more UVB rays will be available year-round if you're closer to the equator.

The Importance of Sun Safety

While you can get vitamin D from the sun after 4 p.m., it’s still important to consider the risks of sun exposure. The longer you are outside, the greater your risk of developing skin cancer. For this reason, aim to get your vitamin D from the sun safely and effectively. Use an app like SunSeek to help you optimize your sun exposure and avoid getting too much sun.

Factors That Affect Vitamin D Synthesis

Geographic Location

People living in more northern latitudes farther away from the equator have lower exposure to the sun. This is due to something called the “solar zenith angle.” The solar zenith angle is the angle between the local zenith (directly above the point where you are on the ground) and the line of sight from that point to the sun. The higher the sun is in the sky and the closer to the equator you are, the lower the solar zenith angle. As the solar zenith angle increases (when the sun gets further away from the highest point in the sky), the amount of UVB rays reaching the earth’s surface is reduced.

At higher latitudes—which have a greater distance from the equator—more UVB radiation is absorbed by the ozone layer, meaning it’s less able to reach our skin. In general, the further you get from the equator, the lower the vitamin D status of that population. At high latitudes (>40°), the sun does not provide any vitamin D during the winter, making vitamin D supplements, cod liver oil, or a focus on consuming fatty fish essential. For example, people living in Boston (42° North), Edmonton, Canada (52° North), Norway (60° North), and Ushuaia, Argentina (55° South) are all unable to produce significant amounts of vitamin D from the sun for 4 to 6 months of the year.

Skin Color and Type

How much vitamin D you make has a lot to do with your skin color and type. Skin type is based on the Fitzpatrick scale:

Type I: The palest and whitest skin tone that always burns (and quickly) and never tans
Type II: Fair/white and usually burns; sometimes tans, but with difficulty
Type III: Medium, white/olive skin tone; sometimes mildly burns but gradually tans into an olive color
Type IV: Olive/moderate brown; rarely burns and tans easily
Type V: Brown/dark brown; very infrequently burns and tans very easily
Type VI: Black/very dark brown; never burns and tans very easily

People with Type IV (sometimes Type III) and above have more melanin in their skin, which helps to protect the skin against damage from excessive sun. Melanin absorbs UV rays, acting like an internal sunscreen. (However, this does not mean people with darker skin are immune to skin cancer!) While it’s helpful that people with dark skin types don’t burn as quickly, that also means that they don’t produce vitamin D as quickly. Some research suggests that people with darker skin need anywhere from 30 minutes to 2 hours longer in the sun than light-skinned people to get the same amount of vitamin D.

Season and Time of Day

Both the time of year and the time of day affect vitamin D synthesis, which is again related to the sun’s solar zenith angle. The solar zenith angle is increased during the early morning and late afternoon (when the sun is not directly overhead) and during the winter months. The best vitamin D synthesis comes midday, but peak hours are from 10 am to 2 pm. The UV Index needs to be over 3 for our skin to produce significant vitamin D, which often only occurs during these midday hours. In the summer, the peak hours might be extended. When the UV index is three or higher, these are the general recommendations for the maximum amount of time to expose unprotected skin:

Type I: 10 minutes
Type II: 20 minutes
Type III: 30 minutes
Type IV: 50 minutes
Type V and VI: 60 minutes

Midday summer sun exposure will produce the fastest and most significant vitamin D synthesis.

Clothing

The more clothing you wear or cover your body, the less surface area is exposed to the sun’s UVB rays. Although it seems straightforward, there are some caveats here, too. As you may know, if you spend a lot of time outdoors, some clothing is equipped with UPF (UV Protection Factor), while others are not. If you wear UPF clothing, UVB rays will not penetrate the clothing, and you will not get vitamin D under the covered areas. However, some fabrics do let through some UVB rays. For example, a 2014 study found that 100% cotton-knitted fabric allowed for a 15% transmittance of solar UV rays, leading to a slower rate of vitamin D synthesis with reduced sunburn risk. If you want to maximize your 5-30 minutes in the sun, take off as many clothes as reasonably possible (and appropriate!) to get the maximum amount of vitamin D synthesis.

Weight

Excess body weight may affect how the body synthesizes and stores vitamin D. Research has found that obese people have a 57% lower vitamin D synthesis after exposure to whole-body UV radiation and high-dose vitamin D supplementation compared to non-obese BMIs. Although the research isn’t conclusive, one reason might be that subcutaneous adipose tissue has lower expression of one of the enzymes needed to convert inactive vitamin D into its active form. This means that people with more adipose tissue (fat) may have trouble with the conversion process that fully activates vitamin D.

Genetics

Researchers have pinpointed several genes involved in the synthesis and transport pathways related to vitamin D metabolism. Alterations or variants in these genes may affect overall vitamin D status, including how it’s synthesized in the skin. One of the genetic variants involved in vitamin D synthesis is the gene DHCR7 (7-Dehydrocholesterol Reductase). From our biochem lesson earlier, 7-dehydrocholesterol is the form of cholesterol in our skin that reacts with UVB rays to synthesize vitamin D. DHCR7 encodes for the enzyme that helps the conversion of 7-dehydrocholesterol into cholesterol. People with boosted gene expression will have increased conversion rates, which reduces the availability of 7-dehydrocholesterol in the skin for UVB rays to interact with. Other genes may also be altered, including those related to vitamin D receptors, vitamin D binding proteins, transport proteins, and cholesterol metabolism.

Sunscreen Use

Some researchers think the rise in sunscreen use over the past 50 years is why vitamin D deficiency is so prevalent in modern society. Conversely, other researchers state that sunscreen typically does not significantly inhibit vitamin D synthesis (which may be in part because people apply sunscreen so poorly). While sunscreen is undoubtedly essential to protect against skin cancer and sun damage, there is a middle ground many of us can take to optimize our vitamin D synthesis while still protecting ourselves.

Most studies have used a lower SPF (like SPF 15), which still allows for some vitamin D production. It’s also important to note that only broad-spectrum sunscreen (that blocks both UVA and UVB rays) would affect vitamin D, as we only make it in our skin upon exposure to UVB. The authors of a review in the British Journal of Dermatology conclude, “Judicious use of daily broad‐spectrum sunscreens with high ultraviolet (UV) A protection will not compromise vitamin D status in healthy people.”

However, they also state that people using high-SPF sunscreens, protective clothing, or shade-seeking behavior are more likely to have compromised vitamin D status. Other research states that sunscreens with an SPF of 30 will absorb approximately 95% of incident UVB radiation, reducing vitamin D production in the skin by about 95%. Overall, a moderate broad-spectrum sunscreen with higher UVA protection (~SPF 15) will likely not affect vitamin D synthesis, and daily sunscreen is always recommended to protect against skin cancer, skin damage, and premature aging.

That said, getting 5-30 minutes of unprotected sunlight exposure (depending on your skin type and propensity to burn) without sunscreen is the best way to raise vitamin D levels. If you are worried about premature aging, always apply sunscreen to your face and instead use your arms.

Can You Get Vitamin D from the Sun at 5 PM?

According to the National Institutes of Health, between five and 30 minutes of sun exposure to your unprotected face, arms, legs, or back between 10 a.m. and 3 p.m. two to three times every week is enough for your body to produce all of the D3 it needs. Sunscreen can block vitamin D production.

Download Our App to Track your Daily Sunlight Exposure Today

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SunSeek helps you optimize your daily sunlight exposure by tracking and providing personalized recommendations based on your location, skin type, and health goals. The app combines real-time UV monitoring with guided outdoor activities to help you improve sleep, boost energy levels, and maintain optimal vitamin D levels throughout the year. By aligning your daily routine with natural light cycles, SunSeek makes it easy to utilize sunlight's health benefits while ensuring safe exposure through personalized timing recommendations and cloud coverage forecasts. Download our app now to track your daily sunlight exposure.